1. Field of the Invention
The present invention relates to an improvement in DC lighting, and more particularly to a device for alternating the polarity of a DC power signal prior to powering a fluorescent bulb.
2. Description of Related Art
Conventional fluorescent lighting systems may operate from either AC or DC power. However, if AC power is applied to a fluorescent tube, the alternating signal results in flickering of the light given off by the bulb. Over a period of time, flickering may result in harm to the eyes. Conventional DC fluorescent lighting systems solve this problem by applying a constant signal to the fluorescent bulb, thereby continuously driving the bulb. Since the driving signal does not alternate there is no flickering of the light given off by the bulb. Despite the great advantage of the DC fluorescent lighting system a significant problem is presented. If the fluorescent bulb is always biased by the DC power signal in the same directions severe aging and degradation of the cathode results. It would be greatly advantageous to provide a device for alternating the polarity of the DC power signal upon application to the fluorescent bulb which does not cause a significant amount of flicker. Such a device would prevent premature aging of the cathode of the bulb and yet provide a constant lighting source.
Accordingly, it is an object of the present invention to provide a circuit for selectively alternating the polarity of a DC power signal applied to a fluorescent bulb each time power is applied to the bulb.
It is another object of the present invention to alternate the aforesaid polarity by both manually and electrically operated means.